Two dimensional array in python

Question

I want to know how to declare a two dimensional array in Python.

arr = [[]]

arr[0].append(\"aa1\")
arr[0].append(\"aa2\")
arr[1].append(\"bb1\")
arr[1].appe         


        

Answer 1

What you're using here are not arrays, but lists (of lists).

If you want multidimensional arrays in Python, you can use Numpy arrays. You'd need to know the shape in advance.

For example:

 import numpy as np
 arr = np.empty((3, 2), dtype=object)
 arr[0, 1] = 'abc'

Answer 2

We can create multidimensional array dynamically as follows,

Create 2 variables to read x and y from standard input:

 print("Enter the value of x: ")
 x=int(input())

 print("Enter the value of y: ")
 y=int(input())

Create an array of list with initial values filled with 0 or anything using the following code

z=[[0 for row in range(0,x)] for col in range(0,y)]

creates number of rows and columns for your array data.

Read data from standard input:

for i in range(x):
         for j in range(y):
             z[i][j]=input()

Display the Result:

for i in range(x):
         for j in range(y):
             print(z[i][j],end=' ')
         print("\n")

or use another way to display above dynamically created array is,

for row in z:
     print(row)

Answer 3

When constructing multi-dimensional lists in Python I usually use something similar to ThiefMaster's solution, but rather than appending items to index 0, then appending items to index 1, etc., I always use index -1 which is automatically the index of the last item in the array.

i.e.

arr = []

arr.append([])
arr[-1].append("aa1")
arr[-1].append("aa2")

arr.append([])
arr[-1].append("bb1")
arr[-1].append("bb2")
arr[-1].append("bb3")

will produce the 2D-array (actually a list of lists) you're after.

Answer 4

a = [[] for index in range(1, n)]